| 1. |
- Eklund, Anders, 1965-, et al.
(författare)
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A catheter tactile sensor for measuring hardness of soft tissue : measurement in a silicone model and in an in vitro human prostate model
- 1999
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Ingår i: Medical and Biological Engineering and Computing. - 0140-0118 .- 1741-0444. ; 37:5, s. 618-624
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Tidskriftsartikel (refereegranskat)abstract
- Tissue hardness is related to tissue composition, and this is often changed by disease. It is therefore of interest to measure the hardness in an objective and non-invasive way. A tactile sensor based on a vibrating piezoelectric ceramic element in a feedback loop is described. When the sensor touches an object it produces a frequency shift related to the hardness of the object. The aim of this study was to develop an in vitro hardness measurement method using a catheter type version of the sensor. The method was evaluated in an established silicone tissue model and on human prostate tissue in vitro. A linear relationship was found with a high degree of explanation (R2 = 0.98) between a cone penetration hardness standard (DIN ISO 2137) applied to the silicone model and the corresponding frequency shift. The results from measurements on a human prostate tissue sample, fixed with formalin, showed that the relative hardness measured with the tactile sensor correlated (R = -0.96, p < 0.001, N = 60) with the proposed hardness related to the histological composition of the prostate tissue. The results indicated that hardness of prostate tissue, and maybe hardness of human tissue in general, can be expressed according to the cone penetration standard and that the hardness can be measured with this tactile sensory system. These findings hold the promise of further development of a non-invasive tool for hardness measurement in a clinical situation
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| 2. |
- Eklund, Anders, 1965-, et al.
(författare)
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A resonator sensor for measurement of intraocular pressure : evaluation in an in vitro pig-eye model
- 2000
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Ingår i: Physiological Measurement. - : IOP Publishing. - 0967-3334 .- 1361-6579. ; 21:3, s. 355-367
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Tidskriftsartikel (refereegranskat)abstract
- Intraocular pressure (IOP) measurement is performed routinely at every eye clinic. High IOP, which can be a sign of glaucoma, can lead to degeneration of the retina and can cause blindness. In this study we developed a resonator sensor for IOP measurement based on an oscillator consisting of a piezoelectric element made of lead zirconate titanate, a flat contact piece of nylon and a feedback circuit. The aim of this study was to evaluate the new sensor's ability to determine lOP in an in vitro pig-eye model. Six eyes from four pigs were removed and fixed in agar. They were then pressurized by a saline column (10-35 cm H2O) through a cannula inserted into the vitreous chamber. The IOP was measured with the resonator sensor applied to cornea. An Alcon applanation pneumatonometer and a standard Viggo-Spectramed pressure sensor connected to the saline column were used as references. The IOP as measured with the resonator sensor correlated well with the pressure elicited by the saline column for individual eyes (r = 0.96-0.99, n = 60) and for all eyes (r = 0.92, n = 360). The correlation between the resonance sensor and the pneumatonometer was r = 0.92 (n = 360). The pneumatonometer also showed a good correlation with the saline column (r = 0.98, n = 360). We conclude that our in vitro pig-eye model made it possible to induce reproducible variation in IOP, and measurement of that pressure with the newly developed resonator sensor gave very promising results for development of a clinically applicable IOP tonometer with unique properties.
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| 3. |
- Nyberg, Morgan, et al.
(författare)
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A combined tactile and Raman probe for tissue characterization - Design considerations
- 2012
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Ingår i: Measurement Science and Technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 23:6
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Tidskriftsartikel (refereegranskat)abstract
- Histopathology is the golden standard for cancer diagnosis and involves the characterization of tissue components. It is labour intensive and time consuming. We have earlier proposed a combined fibre-optic near-infrared Raman spectroscopy (NIR-RS) and tactile resonance method (TRM) probe for detecting positive surgical margins as a complement to interoperative histopathology. The aims of this study were to investigate the effects of attaching an RS probe inside a cylindrical TRM sensor and to investigate how laser-induced heating of the fibre-optic NIR-RS affected the temperature of the RS probe tip and an encasing TRM sensor. In addition, the possibility to perform fibre-optic NIR-RS in a well-lit environment was investigated. A small amount of rubber latex was preferable for attaching the thin RS probe inside the TRM sensor. The temperature rise of the TRM sensor due to a fibre-optic NIR-RS at 270 mW during 20 s was less than 2 degrees C. Fibre-optic NIR-RS was feasible in a dimmed bright environment using a small light shield and automatic subtraction of a pre-recorded contaminant spectrum. The results are promising for a combined probe for tissue characterization.
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| 4. |
- Y Banaem, Hossein, et al.
(författare)
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Brain tumor modeling : glioma growth and interaction with chemotherapy
- 2011
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Ingår i: International Conference on Graphic and Image Processing (ICGIP 2011). - : SPIE. ; 8285
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Konferensbidrag (refereegranskat)abstract
- In last decade increasingly mathematical models of tumor growths have been studied, particularly on solid tumors which growth mainly caused by cellular proliferation. In this paper we propose a modified model to simulate the growth of gliomas in different stages. Glioma growth is modeled by a reaction-advection-diffusion. We begin with a model of untreated gliomas and continue with models of polyclonal glioma following chemotherapy. From relatively simple assumptions involving homogeneous brain tissue bounded by a few gross anatomical landmarks (ventricles and skull) the models have been expanded to include heterogeneous brain tissue with different motilities of glioma cells in grey and white matter. Tumor growth is characterized by a dangerous change in the control mechanisms, which normally maintain a balance between the rate of proliferation and the rate of apoptosis (controlled cell death). Result shows that this model closes to clinical finding and can simulate brain tumor behavior properly.
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| 5. |
- Böhler, Christian, et al.
(författare)
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Multilayer Arrays for Neurotechnology Applications (MANTA): Chronically Stable Thin-Film Intracortical Implants
- 2023
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Ingår i: Advanced Science. - : John Wiley & Sons. - 2198-3844. ; 10:14
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Tidskriftsartikel (refereegranskat)abstract
- Flexible implantable neurointerfaces show great promise in addressing one of the major challenges of implantable neurotechnology, namely the loss of signal connected to unfavorable probe tissue interaction. The authors here show how multilayer polyimide probes allow high-density intracortical recordings to be combined with a reliable long-term stable tissue interface, thereby progressing toward chronic stability of implantable neurotechnology. The probes could record 10–60 single units over 5 months with a consistent peak-to-peak voltage at dimensions that ensure robust handling and insulation longevity. Probes that remain in intimate contact with the signaling tissue over months to years are a game changer for neuroscience and, importantly, open up for broader clinical translation of systems relying on neurotechnology to interface the human brain.
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| 6. |
- Yousefi, Hossein, et al.
(författare)
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An optimised linear mechanical model for estimating brain shift caused by meningioma tumours
- 2013
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Ingår i: International Journal of Biomedical Science and Engineering. - : Science Publishing Group. - 2376-7227 .- 2376-7235. ; 1:1, s. 1-9
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Tidskriftsartikel (refereegranskat)abstract
- Estimation of brain deformation plays an important role in computer-aided therapy and image-guided neurosurgery systems. Tumour growth can cause brain deformation and change stress distribution in the brain. Biomechanical models exist that use a finite element method to estimate brain shift caused by tumour growth. Such models can be categorised as linear and non-linear models, both of which assume finite deformation of the brain after tumour growth. Linear models are easy to implement and fast enough to for applications such as IGS where the time is a great of concern. However their accuracy highly dependent on the parameters of the models in this paper, we proposed an optimisation approach to improve a naive linear model to achieve more precise estimation of brain displacements caused by tumour growth. The optimisation process has improved the accuracy of the model by adapting the brain model parameters according to different tomour sizes.We used patient-based tetrahedron finite element mesh with proper material properties for brain tissue and appropriate boundary conditions in the tumour region. Anatomical landmarks were determined by an expert and were divided into two different sets for evaluation and optimisation. Tetrahedral finite element meshes were used and the model parameters were optimised by minimising the mean square distance between the predicted locations of the anatomical landmarks derived from Brain Atlas images and their actual locations on the tumour images. Our results demonstrate great improvement in the accuracy of an optimised linear mechanical model that achieved an accuracy rate of approximately 92%.
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| 7. |
- Candefjord, Stefan, et al.
(författare)
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Combining fibre optic Raman spectroscopy and tactile resonance measurement for tissue characterization
- 2010
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Ingår i: Measurement science and technology. - : IOP Publishing Ltd. - 0957-0233 .- 1361-6501. ; 21:125801, s. 1-8
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Tidskriftsartikel (refereegranskat)abstract
- Tissue characterization is fundamental for identification of pathological conditions. Raman spectroscopy (RS) and tactile resonance measurement (TRM) are two promising techniques that measure biochemical content and stiffness, respectively. They have potential to complement the golden standard-–histological analysis. By combining RS and TRM, complementary information about tissue content can be obtained and specific drawbacks can be avoided. The aim of this study was to develop a multivariate approach to compare RS and TRM information. The approach was evaluated on measurements at the same points on porcine abdominal tissue. The measurement points were divided into five groups by multivariate analysis of the RS data. A regression analysis was performed and receiver operating characteristic (ROC) curves were used to compare the RS and TRM data. TRM identified one group efficiently (area under ROC curve 0.99). The RS data showed that the proportion of saturated fat was high in this group. The regression analysis showed that stiffness was mainly determined by the amount of fat and its composition. We concluded that RS provided additional, important information for tissue identification that was not provided by TRM alone. The results are promising for development of a method combining RS and TRM for intraoperative tissue characterization.
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| 8. |
- Candefjord, Stefan, et al.
(författare)
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Combining scanning haptic microscopy and fibre optic Raman spectroscopy for tissue characterization
- 2012
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Ingår i: Journal of Medical Engineering & Technology. - : Taylor & Francis. - 0309-1902 .- 1464-522X. ; 36:6, s. 319-327
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Tidskriftsartikel (refereegranskat)abstract
- The tactile resonance method (TRM) and Raman spectroscopy (RS) are promising for tissue characterization in vivo. Our goal is to combine these techniques into one instrument, to use TRM for swift scanning, and RS for increasing the diagnostic power. The aim of this study was to determine the classification accuracy, using support vector machines, for measurements on porcine tissue and also produce preliminary data on human prostate tissue. This was done by developing a new experimental set-up combining micro-scale TRMscanning haptic microscopy (SHM)for assessing stiffness on a micro-scale, with fibre optic RS measurements for assessing biochemical content. We compared the accuracy using SHM alone versus SHM combined with RS, for different degrees of tissue homogeneity. The cross-validation classification accuracy for healthy porcine tissue types using SHM alone was 6581%, and when RS was added it increased to 8187%. The accuracy for healthy and cancerous human tissue was 6770% when only SHM was used, and increased to 7277% for the combined measurements. This shows that the potential for swift and accurate classification of healthy and cancerous prostate tissue is high. This is promising for developing a tool for probing the surgical margins during prostate cancer surgery.
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| 9. |
- Candefjord, Stefan
(författare)
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Combining the tactile resonance method and Raman spectroscopy for tissue characterization towards prostate cancer detection
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Prostate cancer (PCa) is the most common male cancer in Europe and the US, and only lung and colorectal cancer have a higher mortality among European men. In Sweden, PCa is the most common cause of cancer-related death for men.The overall aim of this thesis was to explore the need for new and complementary methods for PCa detection and to take the rst step towards a novel approach: combining the tactile resonance method (TRM) and Raman spectroscopy (RS). First, the main methods for PCa detection were reviewed. Second, to establish a robust protocol for RS experiments in vitro, the eects of snap-freezing and laser illumination on porcine prostate tissue were studied using RS and multivariate statistics. Third, measurements on porcine and human tissue were performed to compare the TRM and RS data via multivariate techniques, and to assess the accuracy of classifying healthy and cancerous tissue using a support vector machine algorithm.It was concluded through the literature review that the gold standard for PCa detection and diagnosis, the prostate specic antigen test and systematic biopsy, have low sensitivity and specicity. Indolent and aggressive tumors cannot be reliably dierentiated, and many men are therefore treated either unnecessarily or too late. Clinical benets of the state-of-the-art in PCa imaging - advanced ultrasound and MR techniques - have still not been convincingly shown. There is a need for complementary and cost-eective detection methods. TRM and RS are promising techniques, but hitherto their potential for PCa detection have only been investigated in vitro.In the RS study no evidence of tissue degradation due to 830 nm laser illumination at an irradiance of ∼3 · 1010 W m-2 were found. Snap-freezing and subsequent storage at -80° C gave rise to subtle but signicant changes in Raman spectra, most likely related to alterations in the protein structure. The major changes due to PCa do not seem to be related to the protein structure, hence snap-freezing may be applied in our experiments.The combined measurements on porcine and human prostate tissue showed that RS provided additional discriminatory power to TRM. The classication accuracy for healthy porcine prostate tissue, and for healthy and cancerous human prostate tissue, was > 73%. This shows the power of the support vector machine applied to the combined data.In summary, this work indicates that an instrument combining TRM and RS is a promising complementary method for PCa detection. Snap-freezing of samples may be used in future RS studies of PCa. A combined instrument could be used for tumor-border demarcation during surgery, and potentially for guiding prostate biopsies towards lesions suspicious for cancer. All of this should provide a more secure diagnosis and consequently more effcient treatment of the patient.
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| 10. |
- Candefjord, Stefan, et al.
(författare)
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Evaluating the use of a Raman fiberoptic probe in conjunction with a resonance sensor for measuring porcine tissue in vitro
- 2009
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Ingår i: IFMBE Proceedings of the World Congress on Medical Physics and Biomedical Engineering. - Heidelberg : Springer. ; , s. 414-417, s. 414-417
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Konferensbidrag (refereegranskat)abstract
- Prostate cancer is the most common form of cancer and is the third leading cause of cancer-related death in European men. There is a need for new methods that can accurately localize and diagnose prostate cancer. In this study a new approach is presented: a combination of resonance sensor technology and Raman spectroscopy. Both methods have shown promising results for prostate cancer detection in vitro. The aim of this study was to evaluate the combined information from measurements with a Raman fiberoptic probe and a resonance sensor system. Pork belly tissue was used as a model system. A three-dimensional translation table was equipped with an in-house developed software, allowing measurements to be performed at the same point using two separate instruments. The Raman data was analyzed using principal component analysis and hierarchical clustering analysis. The spectra were divided into 5 distinct groups. The mean stiffness of each group was calculated from the resonance sensor measurements. One of the groups differed significantly (p < 0.05) from the others. A regression analysis, with the stiffness parameter as response variable and the principal component scores of the Raman data as the predictor variables, explained 67% of the total variability. The use of a smaller resonance sensor tip would probably increase the degree of correlation. In conclusion, Raman spectroscopy provides additional discriminatory power to the resonance sensor.
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